One of the main aims of this group has been to develop a reliable animal model for the study of drug-induced aplastic anemia. After investigating a number of common laboratory animal models for induction of aplastic anemia by chloramphenical, we concluded that none of them would serve for the specific purpose. Since calves have been used for the study of aplastic anemia induced by feeding trichloroethylene extracted soyabean meal, we have utilized calves for chloramphenicol and trichloroethylene induced aplastic anemia. Even though chloramphenicol produces only a milder form of aplastic anemia compared to trichloroethylene and its glutathione (cysteine) conjugate, namely dichlorovinyl cysteine, which induces a complete bone marrow aplasia, it is possible that by changing certain conditions it may be possible to induce a complete aplasia in bone marrow by chloramphenicol treatment. By using this animal model and its bone marrow cells in culture we hope to gain a better understanding of the biochemical mechanism involved in drug-induced aplastic anemia.